1  /****
   2   *
   3   * This program computes simple statistics for five real numbers read from
   4   * standard input.  The statistics computed are the sum of the numbers, the
   5   * arithmetic mean, and the standard deviation.  The results are output to
   6   * standard output, in the following form:
   7   *
   8   * Sum = 
   9   * Mean =
  10   * Standard Deviation =
  11   *
  12   * Author: Gene Fisher (gfisher@calpoly.edu)
  13   * Created: 31mar11
  14   * Last Modified: 31mar11
  15   *
  16   */
  17  
  18  #include <stdio.h>
  19  #include <math.h>
  20  
  21  #define NUM_DATA_POINTS 5               /* Fixed number of data points */
  22  
  23  int main () {
  24  
  25      double x1, x2, x3, x4, x5;          /* Input variables */
  26      double sum;                         /* Computed sum */
  27      double mean;                        /* Computed mean */
  28      double std_dev;                     /* Computed standard deviation */
  29  
  30      /*
  31       * Prompt the user for the input.
  32       */
  33      printf("Enter five real numbers, separated by spaces: ");
  34  
  35      /*
  36       * Input the numbers.
  37       */
  38      scanf("%lf%lf%lf%lf%lf", &x1, &x2, &x3, &x4, &x5);
  39  
  40      /*
  41       * Compute the sum.
  42       */
  43      sum = x1 + x2 + x3 + x4 + x5;
  44  
  45      /*
  46       * Compute the mean.
  47       */
  48      mean = sum / NUM_DATA_POINTS;
  49  
  50      /*
  51       * Compute the standard deviation.
  52       */
  53      std_dev = sqrt((pow(x1 - mean, 2) +
  54                      pow(x2 - mean, 2) +
  55                      pow(x3 - mean, 2) +
  56                      pow(x4 - mean, 2) +
  57                      pow(x5 - mean, 2)) / (NUM_DATA_POINTS - 1 ));
  58  
  59      /*
  60       * Output the results.
  61       */
  62       printf("Sum = %f\n", sum);
  63       printf("Mean = %f\n", mean);
  64       printf("Standard Deviation = %f\n\n", std_dev);
  65  
  66      return 0;
  67  
  68  }